How does Smooth effect polycounts?

[orcus]

Smoothing groups just smooth the shading of the model, they dont affect the geometry. They are normally used in 3d game engines... but it depends on engine if it supports smoothing groups that are used in max or it have own smoothing group and dont support importing of smoothing groups.
(I hope u understand me, my knowledge of english is just basic...)

[Serial]

it doesn't affect your polycount in any way. if your game-engine supports gouraud shading everything will be fine

[AdamAtomic]

"smooth" tells the renderer to use the vertex normals and average their values in a linear way across the face of the polygon, to get a smoother look. This is called "gouraud" shading, and nearly all 3d engines support it. It does not affect the poly count at all! In the flat-shaded model, it just uses the face normal from the center of the face to calculate the lighting, instead of the vectors at the 4 corners.

Googled: http://freespace.virgin.net/hugo.elias/graphics/x_polygo.htm

[ArYeS]

In the very lame words:
Engine shades all smoothed polys together, not one by one (that gives bad looking lines)

[MatiasJ]

Sweet! thanks for the answers guys!! Cleared it perfectly in my mind! Thats pretty cool, I felt sure it would be a big hit somewhere and I'd be left with a chunky finish! Once again cheers for the help, much appreciated to all!
-matias

[Ghostscape]

Smoothing groups do not affect your poly count. They do affect your vertice count.

Smooth quad:

1------2
| / |
| / |
| / |
| / |
3------4

With triangles consisting of verts (1,2,3) and (2,4,3).

Creased/Sharp/Whatever quad:

1-----24
| / |
| / |
| / |
| / |
35-----6

With triangles consisting of verts (1,2,3) and (4,5,6).

To explain this without getting too technical: Vertex lighting is handled by calculating the angle of the vert's normal (An imaginary line that points out from the the vert in the direction it is facing) compared the the angle of the light hitting the vert. The larger the angle, the less light. When you smoothshade, one vert is used with a normal that is averaged between the two different triangle's facing directions. To get a sharp edge, you must have two different verts facing in two different directions.

Additionally, you need 2 verts along a texture seam, as each vert can only hold 1 UV coordinate.

Graphics cards do not really care about the number of triangles, but rather the number of vertices, but that is a much more difficult number to manage and track, and thus the industry standard is poly count, not vert count.

A smoothed geosphere with 80 triangles would have 42 vertices, because each triangle after the first one can share two of the previous vertices. An unsmoothed geosphere would require 3 verts for each triangle and therefore would have 240 vertices. 3ds Max does not accurately track this vert count to my knowledge however.

Should you worry about vert count versus polycount? I'd argue you shouldn't really worry about it, because you're going to smooth as much as is aesthetically possible anyways, and you're going to stitch textures together as much as possible anyways, so it isn't really that important. Still it's something to think about.

[MatiasJ]

Thanks Ghostscape, pretty complex but I think I get it! haha, thanks for the reply, its interesting to learn all the stuff that goes on under the bonnet, so to speak, even if it takes a bit to understand!

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